John clark



Canard sans @wat utiliteit.

JOHN CLARK, or HARRISBRQ, PENNSYLVANIA.

Leners Patenten. 103,140, camz May 17, 1870.

rMPRovnMsNT 1N HSTori-PecansG.`

TheSchedule referred to in these Letters Patent and making part of the same.

To all .whom it muy conccrn 5 Be it known that `I, JOHN CLARK, of Harrisburg,

in the county of Danphin, and 4'Statt-3 of Pennsylvania, haveinvented anew and improved Piston Pack' ing; `and I do hereby declare that the following is a full, clear, and exact descriptiontof `the same, reference e being had to the accompanying drawings making a part,

,of this specification, in which`` Figure lisiaplan of the' pistonhead and packing, with thejfollower removed and Figure 2 is a sectional elevation through the center.

VThe invention consists inthe combination'ofanannular wedge iplaced outside of 'a block that projects fronrthe center of a disk which forms the front face of apistomhead, with such disk, and with a parted ring having an innertransverse taper, and placed outside ,the annularv wedge,andwith an outer parted packinga'ing,and with screws passing through the 'disk and bearing againstI the `annular wedge in such manner that, by means of `the screws, thewedge may `he forced into the tapering ring so as to expand it and the outer packing-'ling Vunt-il a steam-tight joint is formed between the piston and cylinder, theforce with which the packing-ring bears against the interior of. the cylinder' being regulated by means of the screws according as `the pressure of steam within the cylinder is greater or less,

a is the piston-head, from the center of which 'projectsa block, b, which .hasfour recesses, b2, formed in its exterior, arranged cquidistant.

A is an annular wedge placed outside Vthe block b, and having four inwardlprojections, a, which enter corresponding recesses, b, in the block b.

The ofiic of the'projec'tions a is to aiiord bearingsurt'acs against which the set-screw c mayoperate.

Bis a ring with an inner transverse taper, and' a cylindrical exterior which surrounds the wedge-A, tting it closely. v p 7 C C are two parted packing-rings that closely fit the routside of the ring B, and are themselves in contactl with the interior of the cylinder. Hence, when the wedge A is forced into the ring B, the ring isf expanded, and so, also, are the rings C C, and the piston is thus made totighly lit the interior ofthe cylinder in which it travels.

The means by which the wedge A is forced into the Y ring B are screws, c, passed through the disk (l and be'aringupon' theprojections a. i

,The disk dis fastened securely to the block b by means of screws, e, of which there are four. i

On-tnrning the screws c, the requisite pressure is brought to bear upon the wedge A, which pressure 'acts evenly on all parts of the inclosing rings, from the center outward.

I am aware that springs are in use for the purpose of' pressing packing-rings against ,the interiors of cylinders by the intel-position of au annular wedge, but there is an objection to this method of tightening, owing to the fact' that springs act with an invariable force at all times, whereas, the force with which the packing-ring bears against the cylinder should vary according to the pressure of steam; the higher the latter,-- the greater is its tendency to pass the packing-ring from the plenum to the vacuum in the cylinder, and the stronger should be the pressure of the packing. ring to resist this tendency.- My arrangement pro` vides for this necessity, as by the screws c thepressure of the packing-ring may be regulated at pleasure.`

Having lthus described my invention,

Vhat I claim as new, and vdesire to secure by Let-v ters Patent, is- Y The combination ofthe a'ckinfr-rin s4 B O annular wedge'A, disk d, block b, and screws c, whenall# these parts are constructed and arranged to operateas described.

e JOHN CLARK. Witnesses: SARAH CLARK, WALLACE DEWITT.' 

